1. Field of the Invention
The present invention relates to an optical disk, an apparatus for recording a data block on the disk and an apparatus for playing the disk.
2. Description of the Related Background Art
Optical disks such as DVD-ROMs have an information area on the innermost part from which information can be read without using tracking servo control. One example of the information area is a PEP (phase encoding part) as shown in for example, Japanese Patent Publication No. 2543523. The PEP area is formed as a pre-pit train when a master disk for optical disks is manufactured. Identification information such as optical disk type and tracking method is recorded in the PEP area.
As the innermost information area, not only the PEP area but also a BCA (burst cutting area) is known (for example, Japanese Patent Laid-Open Publication No. Hei 10-188361). The BCA area is formed by a bar code on each disk when optical disks are manufactured. For example, in the case of DVD-ROMs, the BCA area is formed by removing a reflection film by a YAG (yttrium aluminum garnet) laser. Identification information such as a serial number for each optical disk is recorded in the BCA area.
Each of the PEP area and the BCA area is necessary to be an area approximately 0.5 mm in width on the optical disk. Therefore, an area approximately 1 mm in width on the innermost part is required for both of these areas. However, if both of the PEP area and the BCA area are formed on an optical disk, a data recording area in which main information such as image and audio signals is recorded is decreased.